This invention relates to a flexible endless belt track for a track-driven vehicle such as a snowmobile or the like and to a method of making such belt tracks. The invention more particularly relates to such a belt track having an improved service life. The invention even more particularly relates to rubber compositions for making belt tracks having improved flexible, low friction and wear resistant surfaces for use with vehicle slider suspension systems and with driving systems in which a driving sprocket comes into moving contact with driving means such as teeth or lugs formed on the inside surface of the belt track.
It has been quite common in the prior art to produce belt tracks for small track-driven vehicles such as snowmobiles in which the tracks are provided with one or two rows of spaced sprocket teeth receiving openings adapted to mesh with the vehicle drive sprockets. More recently, it has been popular to mold driving teeth or lugs on the inside surface of the belt track which operate in conjunction with specially designed sprockets to drive the vehicle with no sprocket teeth-receiving openings being necessary. An example of the latter type construction is disclosed in Irgens U.S. Pat. No. 3,472,563 and in Dodson et al's U.S. Pat. No. 3,781,067. Some tracks utilize a combination of the driving lugs and/or sprocket teeth-receiving openings as is illustrated in Russ, Sr. U.S. Pat. No. 3,575,474. Those skilled in the art are aware that in belt track constructions of the type discussed above, the direct sliding frictional contact between slider suspension and the inner surface of the track results in an excessive amount of wear often necessitating the early replacement of the track.
Illustrative of the problems which have been encountered with the use of the channel member or slider bar is its tendency to wear rapidly at the relatively low temperatures, for example, 150.degree.-200.degree. F. These temperatures are built up by frictional contact during the operation of the vehicle in which no snow or water is available for lubrication. Attempts to find other suitable low friction wear-resistant materials from which to produce the slider bars have not proven to be entirely satisfactory.